Bonded non-woven fibrous products and methods for manufacturing them



BONDED NON-WOVEN FIBROUS PRODUCTS METHODS FOR MANUFACTURING Nathaniel A.Matlin and Benjamin B. Kine, Levittovvn, Pa., assignors to Rohm & HaasCompany, Philadelphia, Pa., a corporation of Delaware v 1 No Drawing.Application August 13, 1956"; 7

Serial No. 603,334 I 11 Claims. ci.1s4-101 Unite a s Pa m"*Q 2,923,653Patented Feb. 2 1960 bonded fibrous products of non-woven character fromfibers which are incapable of felting, whether of natural incapable ofbeing converted into a felted product by normal felting operations. Afurther object of the invention is to provide bonded fibrous products ofnonwoven character wherein'the binder may be substantially uniformlydistributed through the body of the structure and has reduced tendencyto migrate preferentially to the surfaces ofthe structure. Other objectsand advantages of the invention willbe apparent from the descriptionthereof hereinafter. a

In accordance with the present invention, it has been 1 found thataqueous dispersions of water-insoluble polyuseful in the production ofarticles of either fiat or threedimensional shape, including insulatingmaterial and the like as will be described more particularlyhereinafter.

Hereinafter, the expression random array is intended to include thearray of fibers in a carded web wherein partial orientation isfrequently present as well as other arrays in which the fibers are in acompletely haphazard distributional relationship.

Heretofore binders of natural rubber latex and aqueousdispersions ofsynthetic rubbers, such as butadiene copolymerized with styrene,acrylonitrile, and so on have When binders of polyvinyl acetates,chlorides, or their I copolymers are used, the hand becomes papery, bywhich is meant that the product has a crisp, brittlezhand and conveysthe impression of thinness and fragility. It also produces a noise oncrumpling that is typical of papers. The application of thermoplasticpolymers such as simple esters of acrylic or methacrylic acid producesproducts in which the binder remains permanently thermoplastic withconsequent tendency to change when subjected toexcessive temperatures.The simple acrylic and methacrylic acid esters are also characterized byrelatively poor adhesion to hydrophobic types of fibers, such as nylon,vinyl resin fibers, cellulose esters and such polyesters, as polyethylene glycol 'terephthalate. Furthermore, many of the bindersheretofore employed, including the aqueous mers of certainhydroxyl-containing esters or amides,

which dispersions also contain a water-soluble aminoplast are capable ofbonding fibers of a non-woven fibrous product and can be converted tosolvent-resistant and wash-resistantfcondition by a simple heatingoperation. The

binder of the present invention comprises a water-insoluble linearpolymer comprising at least 3% by weight of units derived from themonomer of Formula I:

( I o v where I *R is selected from the group consisting of H and CH Ris selected from the-group-co'nsisting of straight and branched chainalkylene groups having 2 to 6 carbon atoms, and -(C,,'H ,,O),,,C,,Hgroups where n is an integer having a value of 2 to 3, and m is aninteger having a value of 1 to 3, and A is selected from the groupconsisting of O and NH--.

Examples of these monomers are:-

fl-hydroxyethyl acrylate fl-hydroxyethyl methacrylate 'N p-hydroxylethylacrylamide N-fl-hydroxyethyl methacrylamide N-fi-hydroxypropylmethacrylamide N-p-hydroxypropyl acrylamide B-hydroxyethoxyethylacrylate ffi-hydroxyethoxyethyl methacrylate 'y-hydroxypropyl acrylate'y-hydroxypropyl methacrylate ,B-hydroxypropyl acrylate fl-hydroxypropylmethacrylate -hydroxyhexyl methacrylate 6-hydroxyhexyl acrylate Thepolymers must not be water-soluble. Where the hydroxy ester or amidemonomer that is polymerized is of such character that a homopolymerproduced therefrom is appreciably water-soluble, it is necessary tocopolymerize such a monomer with at least one other copolymerizablemonoethylenically unsaturated monomer which is of a character that willrender the final copolymer insoluble in water. Many of thehydroxylcontaining monomers have such a large proportion of invention isto provide a bonded fibrous product of nonis a further-object of thepresent invention to produce hydrophobic groups in theirmolecule thathomopolymers thereof will necessarily be water-insoluble and 'insuchcases, a homopolymercan be applied to the fabrics for accomplishing thepurpose of the invention. Frequently, however, it is preferable fromthe'cost standpoint to copolymerize the hydroxy monomer with a cheaperand more readily available comonomer. Preferred compositions of theinvention are, therefore, those copolymers of from 3 to 30% of thehydroxyl-containing ester or amide monomer or of. a mixture of suchmonomers, the- 3' balance of the copolymer being formed of other lessexpensive comonomers.

The dispersion also contains an aminoplast, namely the low molecularweight or monomeric reaction products of an aldehyde, and especiallyformaldehyde with urea, thiourea, biuret, or other homologues orderivatives thereof, such as N,N-ethyleneurea, N,N'-ethyleneurea, N ,N-dimethylurea, N,N-diethylurea, N,N'-dirnethoxymethyl urea,N,N-dimethoxymethylurea, N,N'-diethoxyethylurea, tetramethoxymethylurea,tetraethoxyethylurea. Similar reaction products of formaldehyde withtriazines, such as melamine may also be employed, such as N,N-dimethylmelamine and alcohol-modified melamine-formaldehyde thermosettingresin condensates, e.g. of methyl and ethyl alcohols, for example,dimethoxymethylmonomethylolmelamine. I I

The auxiliary aminoplast binder is used in anamount up to 25% by weightof the weight of polymer containing hydroxyl groups,. 2 to 11% beingpreferably employed.

There may also be introduced into the system either into the aqueousdispersion of the binder or by separate application to the non-wovenfibrous mat or web before or after application of the aqueous dispersionof the binder, a catalyst for accelerating the curing of thepolymer/aminoplast binder. The catalyst may be used in an amount up to2%, preferably about to 1% on the weight of the aminoplast component.The catalyst used may be selected to avoid excessive deterioration ofthe fibers used in the particular fibrous product, but it is in any casean acidic or potentially acidic material, the latter serving as a latentcatalyst and liberating acid on heating. For example, when cellulosicfibers are employed, a latent ammonium salt, such as ammonium chlorideor diammonium phosphate or a latent amine hydrochloride salt, may beemployed such as the hydrochloride or triethanolamine, monoethanolamine,diethylamine and so on.

The bonding of the fibers is eifected with a clear, substantiallycolorless binder which has good adhesion to all sorts of fibers andfilaments and even to those of siliceous character including glasswhich, in the past, have been difficult to handle because of thedifficulty-of finding colorless materials which are adequately adhesivetoward the siliceous material. The binders of the present invention arealso substantially free of discoloration when subjected to elevatedtemperatures, such as those used for drying, fusing or curing.

The copolymer used in the binder of the present invention contains aplurality of hydroxyl groups by which it is adapted to be insolubilizedand rendered infusible on heating with the aminoplast with or without asuitable catalyst. The insolubilization apparently results from thecross-linking which occurs on reaction of the co olymer and theaminoplast. Hence, the cured or baked fibrous product provides improvedresistance to laundering, drycleaning and spotting, to variouschemicals, and to heat as compared to such aqueous systems, as rubberlatex or aqueous dispersions of synthetic rubbers or acrylic or vinylesters, heretofore applied. The bonded fibrous products of the presentinvention can be heated to a much higher temperature than those of theprior art using the binders mentioned above without sufferingdiscoloration, increase in stiffness or deleterious decomposition. Theyare characterized by excellent resistance to ironing in which operationthey are not subject to tackiness as would betrue of the thermoplasticsheretofore used. The

aminoplast/hydroxy polymer combination binder ap- 1 parently alsoprovides a greater versatility of adhesion in that the binders of thepresent invention are'characterized not onlywith good adhesion tohydreph-ilic fiberslike cotton, regenerated cellulose rayons and thelike, but they are also characterized by excellent adhesion-tohydrophobic types of fibers,- such as the nylons and especially thepolyamide types, the vinylresins such as copolymers of vinylchloride-with vinyl .acetate orfiwith acrylonitrile,

polymers of 70 to acrylonitrile with other monomers such as vinylchloride, vinyl acetate, any of the vinyl pyridines such as 2-vinylpyridine or mixtures of such auxiliary comonomers, polyesters such aspoly(ethylene glycol terephthalate), and cellulose esters such ascellulose acetate, cellulose acetate" propionate, cellulose acetatebutyrate, and so on. Because of the characteristic adhesion ofthe-binder of the present invention to both hydrophilic and hydrophobictypes of fibers, the fibrous products are characterized by excellentresistance to pilling and abrasion. The binder of the present inventionis adapted to be dried and then cured to insoluble and infusiblecondition so that the bonds cannot be disturbed even under severeconditions of heat. The fibrous products using the binder of the presentinvention have the advantage also that theycan-be embossed durably inwet condition or during the first drying but before complete drying Thisis evidenced by the fact that if-the dryingfliseffected on a suctionscreen through which the excess water is drained from the fibrousproduct, the pattern of the screen is permanently imparted to one faceof the product and even calendering under normal procedures andtemperatures does not destroy this pattern effect. While the binder maybe preferentially applied, if desired, to portions of thefibrous'product, such as one or both of the faces thereof, it ischaracteristic of the binder of the present invention that, if suchpreferential treatment is not desired, substantially uniformdistribution may be obtained because of the reduced tendency of thebinder after'initial distribution throughout the body of the fibrousproduct to migrate to thesurfaces thereof during drying;

The cured or insolubilized binders are unaffected by water or organicsolvents, such as styrene, even at molding temperatures, whereby thebonded fibrous products are adapted to be used as molding preforms ormolding inserts forth'e production of'moldedarticles from variousthermosetting resins as willbe pointed out in more detail hereinafter.The binders are also free of cold flow and are resistant 'to'fiow atelevatedtemperatures, whereby shifting of the fibers or filaments inthebonded products is substantially completely prevented even atelevated temperatures during subsequent molding with such productsbeingusedas reinforcing inserts or preforms- In accordancewith theinvention, a fibrous product, the fibers of which may consist entirelyof'non-proteinaceous fibers which are incapable of felting, isimpregnated with theaqueous dispersion of the aminoplast and thewaterins oluble linear polymer 'containingthe hydroxyl groups. Themolecular weight-of'the polymers should be from about 100,000 toabout l0r'nillion.

The fibers are present in the'forr'n' of a so-called' non- Woven mator'web in which-theyare haphazardly distributed; The mat'may' be formedby carding when the fibers are of such a character, 'by"virtue of lengthand flexibility, as to be amenable to the carding operation. Naturalfiberslikejute, sisal, ramie, hemp, and cotton may be used, as well asmany artificial fibers or filaments including rayon, those of celluloseesters such as cellulose acetate, vinyl resin fibers such as those ofpolyvinyl chloride, copolymers of vinyl chloride with vinyl acetate,vinylidene chloride or acrylonitrile containing a major proportion ofvinyl chloride in the polymer molecule, polyacrylonitrile and copolymersof acrylonitrile with vinyl chloride, vinyl acetate, methacrylonitrile,vinyl pyridine, or with mixtures of such comonomers and containing amajor proportion from 75% to of acrylonitrile in-the copolymer molecule;also condensation polymers such-as'polyamides of nylon type, polyesterssuch as ethylene glycol-terephthalate'polymers and the like. The thinweb or fleece obtained fromasingle card may be treated in accordancewith the present invention, but generally it is-necessary, and desirableto superpose a plurality of such Webs to buildup the mat to sufiicientthckness for the end use intended, particularly in the making of heatinsulation. ln building up; such=a mat, alternate layers of carded websmay be disposed with their fiber orientation directions disposed at 60or 90 angles wi respect to intervening layers. I

Mats may also be formed bythe deposition'of fibers, either natural orartificial, from an air stream. Thus, continuous filaments may be fed toa cutter or breaker which discharges the fibers into the discharge sideof a blower. Suitable conduits are provided to guide the fibers to acollecting screen or air-pervious structure for collecting the fibers inthe form desired. The screen may be in the fonn of an endlesstravelingbelt passing through the lower portion of a tower into theupper portion of which the blownfibers are introduced by the conduitwork. A suction box may be'disposed beneath the upper course of thetraveling screen to assist in the deposition of the fibers thereon.Instead of having a traveling flat screen, a stationary formed screenmay be used. For example, it may take the form of a hat-shaped cone suchas that used in the felt hat-making industry. Alternatively, it may haveany other form suitable to produce the desired shape of the fibrousproduct, such as rectangular tray. Again, suction may be applied beneaththe screen to assist deposition of the fibers thereon.

The fibers and filaments may be formed by direct spraying from asolution or molten mass thereof. This is a conventional procedure forthe formation of glass fibers or mineral wool fibers as well as those ofnylon or of thermoplastic materials, such as vinyl resins of the typementioned hereinabove, adapted to be dissolved in a suitable solvent,such as acetone or dimethylformamide, or to be melted. The solution ormelt is, of course, directed to suitable nozzles or jet-forming orificesand a high pressure fluid stream, such as of cold or hot air or of inertgases such as nitrogen or even of steam, is directed against the streamor streams of filament-forming material to disrupt them and coagulatethem as fibers in thevicinity of the or'fices. Electrostatic spinningmethods may also be employed for this purpose. As in the case of the useof blowers, the disrupted and dispersed fibers may be directed to thetop of a settling tower and be allowed to settle, with the aid ofsuction devices, upon a suitable traveling or stationary screen at thebottom of the tower. This procedure is adaptable to the production offibers of siliceous materials such as glass or mineral wool, as well asto thermoplastic resin fibers mentioned above.

Another procedure may involve the extrusion of continuous filaments,either from solutions of the filamentforming material or from moltenmasses thereof, and the cutting or breaking of the filaments to fibersof a predetermined length which may be fed to a hopper at the top of asettling tower into which they may be discharged by conventional feedingdevices, and at the bottom of which a traveling or stationary screen maybe deposited for collection of the fibers.

The fibers and filaments that may be used in the present invention maybe natural or artificial as stated above. The selection of theparticular material of which the fiber is made frequently depends uponthe use intended of the product. For example, siliceous .fibers areextremely valuable in the production of molded articles because of theexceptional strength obtained by their use. However, when the bondedfibrous products are used for filtration purposes, fibers of certainresins may be preferred to provide resistance to attack by acids oralkalies that may be present in the liquids to be filtered. Thus,polymers containing a high percentage of acrylonitrile or of vinylchloride or even of such highly halogenated resins aspolytetrafluoroethylene or poly(chlorotrifluoroethylene) may be moreuseful in such cases. Forcertain purposes, it may be desirable to formthe fibrous products from a mixture of fibers of different types. Anexample is the use of a mixture of thermoplastic fibers of potentiallyadhesive character with other fibers which lack such potentiallyadhesive character. A fibrous product comprising such a mixture may beheated to the appropriate temperature to render the potentially adhesive fibers tacky to effect bindingof the fibers in the product bythis procedure as well as by the binders of the present invention.

' The binder of the present invention is preferably applied in the formof an aqueous dispersion obtained by the addition of an aminoplast withor without a catalyst to an aqueous dispersion of a polymer which may beproduced by the emulsion polymerization of monomers con-- tainlnghydroxyl groups preferably with other mono-- ethylenically unsaturatedcomonomers. Alternatively, a dried powder obtained from thefirst-mentioned dispersion may be dusted or sprayed on to the web or thefibers before, during, or after deposition. The comonomers may beselected to provide various properties in: the binder. Thus, they mayprovide a soft and flexiblehinder or they may provide a hard and stiffbinder which imparts corresponding stiffness to the bonded fibrous.

product. Surprisingly, dispersions of copolymers having T, values of 50C. and over can be effectively employed to form coherent bondednon-woven fabrics, even though these dispersions ordinarily do not formcontinuous films when applied to textile fabrics and dried attemperatures above their respective T values.

Useful comonomers which tend to yield soft and flexible polymers whencopolymerized with one of the hydroxyl monomers mentioned above arethose which yield solid polymers which have a T below 15 to 20 C. The Tvalue referred to is the transition temperature or inflectiontemperature which is found by plotting the modulus. of rigidity againsttemperature. A convenient method for determining modulus of rigidity andtransition temperature is described by I. Williamson, British Plastics.23, 87-90, 102 (September 1950). The T value here. used is thatdetermined at 300 kg./cm.

The preferred monomers which by themselves yield soft polymers aremethyl acrylate, ethyl acrylate, propyl. acrylate, isopropyl acrylate,butyl acrylate, isobutyl acrylate, sec-butyl acrylate, amyl acrylate,isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate,3,5,5- trimethylhexyl acrylate, decyl acrylate, dodecyl acrylate,, cetylacrylate, octadecyl acrylate, octadecenyl acrylate,. n-amylmethacrylate, sec-amyl methacrylate, hexyl methacrylate, 2-ethylbutylmethacrylate, octyl methacrylate, 3,5,5-trimethylhexyl methacrylate,-decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, and butoxyethyl arcrylate or methacrylate,. They are esters of acrylic ormethacrylic acid which acids. may be repre sented by the formula COOHwhere n is. an integer having a value of 1 to 2.

As polymerizable monovinylidene monomers which by themselves form hardpolymers, there may be used alkyl methacrylates having akyl groups ofnot over four carbon atoms, also tert-amyl methacrylate, tert-butyl ortert-arnyf acrylate, cyclohexyl or benzyl acrylate or methacrylate,acrylonitrile, or methacrylonitrile, these constituting a preferredgroup of the compounds forming hard polymers. Styrene, vinyl chloride,chlorosty'rene, vinyl acetate and p-methylstyrene also form hardpolymers. Other specific compounds forming hard" polymers are methylmethacrylate, ethyl methacrylate, propyl methacrylate,. isopropylmethacrylate, butyl methacrylate, sec-butyl; methacrylate, tert-butylmethacrylate, acrylamide, and; methacrylamide.

It is frequently desirable to copolymerize thehydroxyloontainingfmonomer' with a mixture of two or more differentcomonomers, one or more of which are selected from the hard categoryjust mentioned and am The polymers used as binders of'the presentinvention may also be graft orv block copolymers wherein one or more,but not all, of the monomers are first po-lymerized and then one or moreother monomers are copolymerized with the firstpolymer obtained. Thus, ahydroxyl-containing monomer may first be homopolymerized orcopolymerized with one or more, but less than all, of the comonomers tobe introduced into the ultimate copolymer, and then the last monomer ormonomers are added to the system and copolymerized or grafted on to thefirst homopolymer or copolymer formed. The same procedure may be used inreverse order to graft the hydroxyl-containing units on to a previouslyformed homopolymer or copolymer of other monomeric units. Again, aplurality of monomeric units may be introduced in succession and thehydroxyl-group-containing monomer may be introduced at the beginning, atany intermediate stage or at the end as desired.

For certain purposes, the copolymers of the present invention havinga Tof about 30 C. or lower may be preferred. These set on drying at roomtemperature to bind the fibers with a soft flexible binder bridging thefibers at their points of intersection or intercrossing with a firmgrip. Their flexibility adapts the fibrous product to be readilyconformed to shaped contours which may be of value in cases where aninsulating product or mat is desired to be bent into the shape of astructure to be covered therewith as in the wrapping of a pipe orcylindrical vessel. Such wrapping can be effected without extensiverupture of the bonds between the fibers and without excessive compactingof the mat, which thereby largely retains its bulky character withnumerous small air-spaces and high heat-insulating value and issubsequently rendered permanent by the baking operation. However, forcertain purposes, it is preferred to use dispersions of copolymershaving a T of 35 C. or higher, such as from 35 to 100 C. In thepreparation of bonded fibrous products of the present invention, whichare intended to serve as preforms in the making of molded products, theuse of polymers having higher T, values has the advantage that thepreform is much stiffer in character and encounters less risk ofdisturbance of the fibers during the handling of the preform inpreparing it for the molding operation per se.

The dispersions adapted to be used as the binderapplying medium of thepresent invention are most advantageously prepared by emulsifying with adispersing agent and polymerizing, preferably under the influence of afree radical catalyst, a mixture of the monomers of which at least 3percent is a hydroxyl-containing monomer.

Anionic, cationic, and non-ionic emulsifiers or dispersing agents may beused. Less advantageously, waterinsoluble polymers comprising at least3% of hydroxylcontaining monomeric units produced in any other way maybe dispersed in water by means of suitable dispersing agents.

The dispersions may contain as little as 1% and as much as 60% of theresinous copolymer on a weight basis. It is, however, morepractical-hence preferred to produce dispersions which contain about 30to 50%, and preferably 2 to 30%, resin content at which it is readilyadapted to be applied as by spraying, dipping, printing, or by transferrolls.

The binder dispersion or powder may be applied to the dry fibers afterthe formation or deposition of the Web or mat so as to penetratepartially into or completely through the interior of the fibrousproducts. Alternatively, the binder dispersion or powder may be appliedto the fibers as they fall through the settling chamber to their pointof deposition. This is advantageously obtained by spraying the. binderdispersion or powder into the settling chamber at some intermediatepoint between the top and the bottom thereof. By so spraying the fibersas they descend to the point of collection,..it is possible to effect athorough distribution of the binder among the fibers before they arecollected into the product. In the production of certain fibrousproducts wherein a hot molten mass of a polymer, such as nylon or afused siliceous mass or glass, is disrupted by jets of heated air orsteam, the binder dispersion or powder may be sprayed directly on thefibers while still hot and very shortly before their deposition so thatquickly after deposition the binder is set and bonds the fibers inproper relationship. Preferably, however, application of the binderdispersion to the fibrous product is made at room temperature tofacilitate cleaning of the apparatus associated with the application ofthe binder dispersion. The binder dispersion may be applied to one orboth surfaces of the fibrous product or it may be distributed throughthe interior as well.

The binder of the present invention may be applied in conjunction withother binders, such as glue. Similarly, the use of potentially adhesivefibers within the fibrous product may also be resorted to in conjunctionwith the use of a binder of the present invention.

If desired, the aqueous dispersion of the polymer con-' taining hydroxylunits may also contain a wetting agent to assist penetration of thefibrous web or mat to which it is applied, and it may contain either afoaming agent to provide the binder in a foamed condition in the finalproduct or it may contain a defoamer when the'ingredicuts of the aqueousdispersion have a tendency to give rise to foaming, and in a particularcase such foaming is undesirable. The conventional wetting agents, suchas the sodium salt of dioctylsuccinate may be used and the conventionalfoaming and defoaming agents may be employed, such as sodium soaps,including sodium oleate for foaming and octyl alcohol or certainsilicones for defoaming.

Generally, the proportion of the binder of the present invention to theweight of the fiber component of'the fibrous product may vary widelydepending on the character of the product desired. For the production ofpreforms, intended to be converted into molded articles, it is preferredto employ from 2 to 10% of the binder of the present invention based onthe weight of fibers. In the production of insulation masses, the amountof binder employed may fa'-l in the lower part of the range justspecified if the binder is applied primarily adjacent to the surface orsurfaces of the product or if it is applied in conjunction with otherbinders. The aqueous dispersion of the polymer containing the hydroxylgroups is generally applied at a concentration of 2 to 60% solids andpreferably at a concentration of 20 to 40% binder solids by weight.

The fibrous product of non-Woven character may contain from 2 to 400% byweight of binder on the weight of the fibers depending on the purposefor which the product is to be used. When the binder is to serve mainlyto bond the fibers together to form a coherent unitary structure inwhich the maximum porosity is retained in conjunction with a minimumchange of natural fiber hand, there may be employed from 2 to 50% byweight of binder solids on fiber, the lower proportion, of course,giving the maximum porosity possible and providing a minimum change inthe natural fiber hand although even with the larger proportion in thisrange, the porosity is mainly retained and the fiber hand is stillevident. The products thus obtained are quite useful for many sanitaryuses such as table napkins, bibs, table cloths, sanitary napkin covers,disposable diapers, disposable sheets, and surgical dressings andcompresses. It is characteristic of the binder applied in the propor-itions just stated that there is relatively little or no window paning,that is the interstices between fibers are left open leaving a highlyporous bulky product. Of course, the density of the product can'beaffected or modified by the application of pressure. to varying extentsprior to or, in many cases, even after the curing of the product.

Fibrous products of non-woven character using from 40 to 150% by weightof the binder of the present invention on'the weight of the'fiber aregenerally quite useful for garment uses to provide interlining fabricsfor coats, dresses, and so on or to provide outer wearing apparelfabrics, such as blouses, skirts, shirts, etc. The garments made ofthese fabrics need no ironing or pressing to restore their appearance,shape, and hand after hand-washing, machine-laundering, and dryingoperations. Besides the general household and appareluses mentionedabove, fibrous products of the invention, in. which 2 to 100% by weightof binder on the weight of fiber is employed, find many light industrialuses as wiping cloths, lining materials for packaging, as filters, andpackings and gaskets for industrial machinery.

Fibrous products of the present invention in which 100 to 400% by weightof the binder on the weight of fiber is used are especially useful forheavy industrial uses where durability and reisstance to wear aredesired, such as in industrial gaskets, packings, filters, and so on.The products containing 20 to 200% of the binder of the presentinvention on the weight of the fiber are useful as laminating layers,either as interlayers or backing sheets in conjunction with plasticfilms and sheets as of polyethylene, nylon, and so on, or in conjunctionwith textile fabrics of woven, braided, knitted, knotted, or feltedcharacter.

To render the binder infusible, curing at elevated temperatures iseffected. Curing temperatures may be as high as 400 C. for setting thebinder, but preferably are in the range from about 110 C. to 350 C. Thecuring serves to render the binder insoluble and infusible and, asstated hereinabove, may be assisted by the use of an acidic catalyst.

As pointed out hereinbefore, the application of the polymers containinghydroxyl groups is adapted to provide fibrous productshaving a widerange of characteristics. When the binder is present in an amount ofabout 2 to 50% on the weight of the fibers in the fibrous product, thelatter retains a textile hand and can have either a soft or a stifftexture depending on the proportion of hydroxyl groups in the polymerand the characteristics of any cornonomers used in making it. Usingpolymers containing 3 to 10% of units containing hydroxyl groups inconjunction with such cornonomers as result in providing a T value ofthe copolymer of 20 C. or less and preferably not over 5 C., a softresilient texture is obtained in conjunction with a textile feel or handand the cured product is quite resistant to laundering, dry-cleaning andspotting to various chemicals and heat. In all of the fibrous productspreviously mentioned, where the binder may be present in the proportionof 2 to 50% as in the products just mentioned or in larger proportionsup to 400% on the weight of the fiber, the products are characterized byfreedomfrom discoloration and excellent resistance to laundering,dry-cleaning and spotting, to various chemicals, and heat as in ironing,good adhesion of the binder to the fibers, and durability of anyembossed pattern. I

The binder of the present invention is essentially colorless and has theadvantage that it undergoes no discoloration at the elevated temperatureneeded for the drying or baking of the fibrous products or even for theformation of molded articles with the fibrous products of the presentinvention used as preforms and ultimately occurring as a reinforcingcomponent in the molded article. The binder of the present invention isresistant to flow at elevated temperatures so a thermoplastic or'thermosetting resin can be applied and the composite thereby obtainedcan be molded at elevated temperature without appreciably disturbing thedisposition of fibers in the mass. Similarly, the binder is insoluble inwater and organic solvents so that the presence of such matedisturb thedisposition of fibers. Consequently, there is no washing of fibers inthe preform with accompanying tendency to form resin-rich areas andfiber-rich areas in the molded article giving rise to suchnon-uniformity which tends to cause cracking or crazing in the moldedarticles and resulting weakness in the reinforced structure. All ofthese properties render the binder outstandingly valuable in connectionwith siliceous fibers, such as those of glass or mineral wool, in theproduction of preforms adapted to be used for forming molded articles.The siliceous fibers are strongly bonded together by means of thebinders-of the present invention and yet the binder is of such characteras not to prevent proper integration of the siliceous fibers within themass of molding resin. In the molded products, the presence of thebinder has no adverse effect either on the appearance or the strength ofthe final articles. While molding resins or resinforming materials ofnumerous thermoplasitc and thermosetting types may be employed, the useof thermosetting types of polyesters isparticularly advantageous. Such aresin-forming material may comprise an unsaturated polyester (such as apolyester of mixed maleic acid and phthalic acid in a 50-50 molar ratio)with a glycol, such as propylene glycol, dissolved in styrene or othercopolymerizable monoethylenically unsaturated monomers having solventproperties for the low condensed polyester. Most binders heretofore usedin the preforms become discolored during the molding operation andinterfere with the penetration of the molding resin, especially when it,is of a polyester type, so that the fused resin is poorly bonded to theportions of the fibers coated by the binder which in turn is manifestedby a reduced transparency and corresponding lack of continuity andhomogeneity. The binder of the present invention is resistant to suchdiscoloration. In addition, it does not interefere with the penetrationof the resin-forming material to the fibers of the preform during themolding operation. This provides excellent transparency and a highdegree of homogeneity and continuity in the product.

The fibrous products of me present inven.ion are ca pable of numeroususes, many of which have been mentioned above. Thus, the fibrous matsbonded with the improved binders of the present invention may serve asheat or sound insulation materials, as filters for air systems, orliquid systems, as permeable membranes as in storage batteries orelectrolytic condensers, as cushioning or padding materials forupholstering purposes and so forth.

As pointed out hereinabove, fibrous mats or fabrics of siliceous fibersare extremely valuable as reinforcements for molded products using thebonded fibrous mat or fabric as a preform with appropriate moldingpowders or syrups. For example, the bonded mat or the bonded laminarfabric assembly may be introduced into a closed mold system with anappropriate amount of a thermosetting resin powder or liquid, such as ofresin-forming condensates of urea-formaldehyde, melamine-formaldehyde,phenol-formaldehyde or polyesters, such as those described in U.S.Patents 2,255,313 and 2,607,756. From 5 to 45% by weightof the moldedarticle may be composed of the reinforcing fiber network when a mat isused as the preform or, in the case of a fabric reinforcement, from 5 to65% by weight of the molded pro-duct may consist of the composite ofbonded fabric laminations.

The following examples are illustrative of the fibrous products and themethods for making them' in accordance with the present invention andparts and percentages are by Weight unless otherwise indicated:

Example 1 (a) A /25 viscose (3 denier, 1 inch staple)/bleached cotton(middling, inch) carded web weighing about 0.75 ounce/square yard isimpregnated with an aqueous dispersion containing per parts: 1

0.4 part of octylphenoxyethoxysodiumsulfate (wetting agent) 2.5 parts ofdimethylol-N,N'-ethyleneurea 0.1 part silicone antifoam at a wet pick-upof about 600% on the weight of the fibers. The web is dried 1.5 minutesat 225 F., and cured 1.5 minutes at 350 F. The resulting non-wovenfabric is about 33/67 fiber/binder. It is highly porous and has a softand resilient feel.

(b) The procedure of part (a) is repeated with Pyrex glass fibers,except that the carded web weighed /2 ounce per square yard andimpregnation with the aqueous dispersion is effected at a wet pick-up of300%, giving a weight ratio of 53/47 fiber to binder in the final fabricwhich is extremely porous and soft, yet coherent.

Example 2 The procedure of Example 1(a) is repeated using a similaraqueous dispersion containing 25.0 parts of an emulsion copoymer of 95%of n-butyl acrylate with of B-hydroxypropyl methacrylate and the sameaminoplast. A porous, soft and coherent non-woven web is obtained.

Example 3 The procedure of Example 1(a) is repeated using a similaraqueous dispersion containing 25.0 parts of an emulsion copolymer of 87%ethyl acrylate, 5.5% of methyl methacrylate, and 7.5% ofN-p-hydroxyethylmethacrylamide. An exceptionally well-bonded, non-wovenweb is obtained that is highly resistant to solvents and heat.

Example 4 The procedure of Example 1(a) is repeated using a similaraqueous dispersion containing 25.0 parts of an emulsion copolymer of 85%of ethyl acrylate and 15% of N-fl-hydroxyt-butyl acrylamide. A coherentweb like that ,of Example 3 but with a softer hand is obtained.

Example 5 The procedure of Example 4 is repeated on a 50/50 whilenylon/disperse-dyed bright acetate (both fibers 3 denier, 1.5 inchstaple) random web obtained by air-deposition weighing about 1.5 oz./sq.yd. After washing and drying, no ironing or pressing is needed torestore the shape, appearance, or hand of garments, such as blouses madeof the fabric.

Example 6 A 50/50 white viscose/dyed Acrilan (polymer of about 85% to90% acrylonitrile) (both fibers 3 denier, 1.5

inch staple) random web obtained by air-deposition weigh- .ing about1.75 oz./ sq. yd. is impregnated with an aqueous dispersion containingper 100 parts:

25 parts of an emulsion copolymer of 95% n-butyl acrylate and 5% of,8-hydroxypropylmethacrylate 2 parts of t-octylphenoxypolyethoxyethanolcontaining about 35 oxyethylene units (emulsifier and dispersing agent)2.5 parts of urea/formaldehyde/methanol condensate 0.5 part ofdiammonium phosphate 0.5 part of octylphenoxyethoxysodiumsulfate(wetting agent) 0.2 part of silicone antifoam at ca. 300% wet pick-up.Dried 1.5 min. at 225 F., cured 5 min. at 350 'F. Product: 55/45fiber/binder;

good coherence, porous, soft, texile hand.

Example 7 An all nylon (50% l0-,denier,..5.0% B-denier, all 1.5.inch

staple) random web obtained by air-deposition weighing about 1.25oz./sq. yd. is impregnated with an aqueous dispersion containing per 100parts:

25 parts of an emulsion copolymer of 5% of fi-hydroxyethyl acrylate andof n-butyl acrylate 2 parts of t-octylphenoxypolyethoxyethanolcontaining about 35 oxyethylene units (emulsifier and dispersing agent)3.5 parts urea/formaldehyde/methanol condensate 0.5 part diethanolaminehydrochloride 0.5 part octylphenoxyethoxysodiumsulfate (wetting agent)0.2 part silicone antifoam at ca. 200% wet pick-up. Dried 1.5 min. at225 F., cured 3 min. at 350 F. Product: 55/45 fiber/binder; soft,resilient, resistant to laundering and dry-cleaning.

Example 8 The procedure of Example 7 is repeated on air-deposited Websof the following fibers:

1) regenerated cellulose (2.0 denier, 1.5 inch staple) 2 oz./sq. yd.carded web,

(2) 55% polyamide 66 nylon and 45% regenerated cellulose both 5 denier,1.75 inch staple,

(3) 100% cotton (garnetted card .waste, roving and yarns) 4 oz./sq. yd.carded web,

(4) 35% cotton and 65% poly(ethylene glycol terephthalate) 1.25 oz./sq.yd. carded web.

Example 9 The procedure of Example 7 is repeated substituting for theurea condensate, 4 parts of a trimethylolmelamine. A coherent web isobtained.

It is to be understood that changes and variations may be made withoutdeparting from the spirit and scope of the invention as defined in theappended claims.

We claim:

1. As an article of manufacture, a non-woven fibrous product in whichthe fibers are distributed in random array, the fibers of which arepredominantly fibers selected from the group consisting of cellulosicfibers, polyamide fibers, polyester fibers, and vinyl resin fibers,fibers in the product being bonded together by a binder comprising 1) awater-insoluble copolymer having a T value not over 30 C. ofmonoethylenically unsaturated monomeric units comprising 3% to 30% byweight of a compound of the formula:

II c112=o (R) CAROH (I) where and (2) a water-soluble aminoplast, theamount of aminoplas-t being from 2 to 25% by weight of the copolymer,said binder being cross-linked to an-infusible condition in which it isalso insoluble in organic solvents, said product being substantiallyresistant to laundering and dry-cleaning, the amount of binder beingfrom 2% to 400% of the weight of fibers in the product.

2. An article as defined in claim 1 in which the aminoplast is acondensate of formaldehyde with a member selected from the groupconsisting of melamine, urea, and N,N'-ethyleneurea.

3. An article ;as defined in claim 1 in'which the fibers compriseatleast 50% by weight of cellulosic fibers.

4. As an article of manufacture, a non-woven fibrous product ,in whichthe fibers are distributed in random array, the jfibers of which .arepredominantly .fibers .se-

lected from the group consisting of cellulosic fibers, polyamide fibers,polyester fibers, and vinyl resin fibers, fibers in the product beingbonded together by a binder comprising 1) a water-soluble aminoplast and(2) a water-insoluble copolymer having a T value not over 30 C. ofmonoethylenically unsatu ated monomeric units comprising (a) 3% to 30%by weight of a compound of the formula where R is selected from thegroup consisting of H and CH R is selected from the group consisting ofstraight and branched chain alkylene groups having 2 to 6 carbon atoms,and -(C,,H ,,O),,,C,,H groups where n is an integer having a value of 2to 3, and m is an integer having a value of 1 to 3, and

A is selected from the group consisting of --O- and and (b) 97% to 70%respectively of at least one ester of an alcohol having 1 to 4 carbonatoms with an acid of the formula wherein n is an integer having a valueof 1 to 2, the amount of aminoplast being 2% to 25% by weight of thecopolymer, said product being substantially resistant to laundering anddry-cleaning, said polymer being crosslinked to an infusible conditionin which it is also insoluble in organic solvents, the amount of binderbeing from 2% to 400% of the weight of fibers in the product.

5. An article of manufacture as defined in claim 4 in which the compoundof Formula I is fi-hydroxyethyl acrylate.

6. An article of manufacture as defined in claim 4 in which the compoundof Formula I is fl-hydroxypropyl methacrylate.

7. An article of manufacture as defined in claim 4 in which the compoundof Formula I is N-fl-hydroxyethylmethacrylamide.

8. An article of manufacture as defined in claim 4 in which the compoundof Formula I is N-fl-hydroxy-tbutylacrylamide.

9. As an article of manufacture, a non-woven fibrous product in whichthe fibersare distributed in random array, the fibers of which consistentirely of fibers selected from the group consisting of cellulosicfibers, polyamide fibers, polyester fibers, and vinyl resin fibers,

' fibers in the product being bonded together by 2% to 400%, on theweight of fibers, of a cross-linked reaction product of a bindercomprising dimethylol-N,N'-ethyleneurea and a water-insoluble copolymerhaving a T value not over 30 C. of 3% to 30% of fi-hydroxyethyl acrylatewith 97% to 70% of butyl acrylate, said product being substantiallyresistant to laundering and drycleaning.

10. A process of making a non-woven fabric which comprises associatingin random array within a web or mat a mass of fibers comprising apredominant proportion of fibers selected from the group consisting ofcellulosic fibers, polyamide fibers, polyester fibers, and vinyl resinfibers, associating with the fibers an aqueous dispersion containing abinder comprising (1) 2 to 60% by weight of a water-insoluble copolymerhaving a T, value not over 30 C. of monoethylenically unsaturatedmonomeric units comprising 3 to 30% by weight of a com- 7 pound of theformula:

CH1=C (R) iABPOH (I) where R is selected from the group consisting of Hand CH R is selected from the group consisting of straight and branchedchain alkylene groups having 2 to 6 carbon atoms, and (C H O),,,C,,Hgroups where n is an integer having a value of 2 to 3, and m is aninteger having a value of 1 to 3, and

A is selected from the group consisting of O and NH, I

and (2) from 2 to 25 by weight, based on the weight of the copolymer, ofa water-soluble aminoplast, drying the fibrous mass containing thebinder at a temperature above the T of the polymer to effect fusion ofthe copolymer and bonding of the fibers thereby and heating the driedfibrous product at a temperature of 110 to 350 C. to render the binderinsoluble in organic solvents,

11. A process of making a non-woven fabric which comprises associating,in random array within a web or mat, a mass of fibers comprising apredominant proportion of fibers selected from the group consisting ofcellulosic fibers, polyamide fibers, polyester fibers, and vinyl resinfibers, bringing into contact with the fibers a binder comprising anaqueous dispersion containing (1) a watersoluble aminoplast and (2) 2%to 60% by weight of a water-insoluble copolymer, having a T value notover about 30 C., of (a) 3% to 30% by weight of a compound of theformula R is selected from the group consisting of H and CH R visselected from the group consisting of straight and 7 of aminoplast being2% to 25 by weight of the copolymer, drying the fibrous mass containingthe binder at a temperature above the T of the polymer to effect fusionof the polymer and bonding of the fibers thereby, and heating the driedfibrous product at a temperature of to 350 C. to render the binderinsoluble in organic solvents.

References Cited in the file of this patent UNITED STATES PATENTS2,256,034 Nottebohm Sept. 16, 1941 2,338,960 Nottebohm Jan. 11, 19442,681,897 Frazier et al June 22, 1954 2,719,795 Nottebohm Oct. 4, 19552,823,142 Sumner et al. Feb. 11, 1958 OTHER REFERENCES Ser. No. 202,136,Nottebohm (A.P.C.), published May 11, 1943.

Ser. No. 306,031, Nottebohm (ARC), published May 11, 1943. l

11. A PROCESS OF MAKING A NON-WOVEN FABRIC WHICH COMPRISES ASSOCIATING,IN RANDOM ARRAY WITHIN A WEB OR MAT, A MASS OF FIBERS, COMPRISING APREDOMINANT PROPORTION OF FIBERS SELECTED FROM THE GROUP CONSISTING OFCELLULOSIC FIBERS, POLYAMIDE FIBERS, POLYESTER FIBERS, AND VINYL RESINFIBERS, BRINGING INTO CONTACT WITH THE FIBERS, A BINDER COMPRISING ANAQUEOUS DISPERSION CONTAINING (1) A WATERSOLUBLE AMINOPLAST AND (2) 2%TO 60% BY WEIGHT OF A WATER-INSOLUBLE COPOLYMER, HAVING A T1 VALUE NOTOVER ABOUT 30*C., OF (A) 3% TO 30% BY WEIGHT OF A COMPOUND OF THEFORMULA